WORLD OF MICROBIOLOGY AND IMMUNOLOGY von Gruber, Max255•
37° C [98.6° F], to match the temperature of its normal intes-
tinal habitat. Refrigeration temperature, which does support
the growth of some bacteria, does not support the growth of
Escherichia coli.
The nature of the growth requirements of bacteria has
been used as a means of grouping bacteria together.
Photoautotrophic bacteria are those that use sunlight as a
source of energy. Heterotrophic bacteriautilize organic carbon
as a type of fuel for growth, while lithotrophic bacteria use
inorganic carbon sources. As a final example, autotrophic bac-
teriaare those bacteria that use carbon dioxide as the only
source of carbon. Similarly, bacteria can be grouped according
to their growth requirements with respect to temperature,
salinity, the hydrogen ion concentration (also known as the
pH), and oxygen.
In the laboratory, growth media often requires the pres-
ence of a few growth factors that the bacteria or other
microbe cannot make themselves. For example, depending on
the particular bacteria being grown, certain amino acids may
need to be supplied. Likewise, the inclusion of compounds
known as purines and pyrimidines may be necessary for the
manufacture of DNA or RNA. Lastly, some vitamins may
need to be added, which allow some enzymesto function.
Sometimes bacteria can become altered so that the daughter
cell has specific nutritional requirements that the parent cell
does not. The mutant strain is referred to as an auxotroph. For
example, a strain of Escherichia colithat requires the amino
acid tryptophane for growth is a tryptophan auxotroph and is
designated as Escherichia coli trp. Auxotrophs can be very
useful as markers, or indicators of the success of an experi-
mental procedure.
Growth of microorganisms can occur in a liquid growth
medium, which is termed a broth, or on a solid medium. Agar
and agaroseare two examples of solid growth media. Often a
broth can be supplemented with the solidifying agent to form
agar. Growth media can be very nonspecific with respect to
nutrients. For example, Brain-Hear Infusion (BHI) broth or
agar is a blended mixture of animal brain and heart. A medium
such as BHI is also referred to as a complex medium. Other
media contains defined amounts of specific components. This
type of medium is also called a minimal medium.
Growth media can also be tailored to favor the growth
of one or a few types of bacteria over the many other types of
bacteria that would develop on a nonselective medium, or to
provide an enriched environment for those bacteria that would
other wise grow poorly or very slowly. An example of a
medium that is both selective and enriched is that used to grow
bacteria in the genus Halococcus. These bacteria require very
high concentrations of salt. The high sodium chloride concen-
tration of the medium is lethal for all other types of bacteria.
In conventional broth and agar cultures, the growth of
microorganisms is uncontrolled. The cells grow as fast as pos-
sible for as long as possible. However, growth of bacteria is
possible such that the rate of growth and division can be con-
trolled. Devices that accomplish this are the chemostat and the
turbidostat. Comparison of the chemical make-up of the same
type of microbe under relatively fast growing or slow growing
conditions can be very useful, particularly because in infec-tions, bacterial growthcan be slower than in the laboratory
environment.See also Agar and agarose; Blood agar, hemolysis, and
hemolytic reactions; Colony and colony formation;
Synchronous growthVONvon Gruber, Max GRUBER, MAX(1853-1927)
Austrian physician and bacteriologistMax von Gruber’s discovery of specific bacterial agglutina-
tion in 1896 laid the groundwork for significant advances in
serologyand immunology.
Gruber was born in Vienna, the son of a prominent
physician, Ignaz Gruber (1803–1872), and his wife, née
Gabrielle Edle von Menninger. His brother, Franz von Gruber
(1837–1918), became famous as an architect, military engi-
neer, and teacher. After preparing for college at the
Schottengymnasium in Vienna, Gruber studied chemistry and
physiology at the University of Vienna, earned his M.D. there
in 1876, then took postgraduate instruction in the biosciences
under Max Josef von Pettenkoffer (1818–1901) in Vienna, Carl
von Voit (1831–1908) and Carl Wilhelm von Nägeli
(1817–1891) in Munich, Germany, and Carl Friedrich Wilhelm
Ludwig (1816–1895) in Leipzig, Germany. Among his fellow
graduate students under Pettenkoffer was Hans Buchner
(1850–1902), who urged Gruber toward bacteriology.
Gruber began lecturing on hygieneat the University of
Vienna in 1882, became professor of hygiene at the
University of Graz, Austria, in 1884, and assumed the same
position in 1887 at the University of Vienna, where he
remained until 1902. He was promoted in 1891 to full profes-
sor. He was unhappy in Vienna because he considered the
facilities ill kept and substandard. Nevertheless, he was able
to attract to Vienna such stellar graduate students as future
Nobel laureate Karl Landsteiner(1868–1943), Alois Lode (b.
1866), and Herbert Edward Durham (1866–1945). From 1902
until he retired in 1923, Gruber was director of the Institute
for Hygiene, Munich.
In March, 1896, Gruber and Durham published a land-
mark article in a prestigious journal, Münchener medizinis-
che Wochenschrift [Munich Medical Weekly], which
described how bacteriaof similar size clump together in
sera, in ways specific to or determined by each serum. Their
research concerned the typhoid bacillus Salmonella typhi,
the cholera bacillus Vibrio cholerae, and the respective sera
of typhoid and cholera patients. This clumping process,
agglutination, soon had wider implications for serology,
immunology, bacteriology, and clinical medicine. The first
important practical consequence of Gruber’s work on bacte-
rial agglutination occurred in June 1896, when the French
physician Georges Fernand Isidor Widal (1862–1929) de-
veloped a diagnostic agglutination test for typhoid, there-
after known as the Gruber-Widal test or the Gruber-Widal
reaction.
In the first decade of the twentieth century, Gruber’s main
interest shifted toward right-wing social theory, political eugen-womi_G 5/6/03 3:18 PM Page 255